This invention relates generally to ultrasonic inspection of dissimilar metal welds, and more particularly ultrasonic inspection of dissimilar metal welds with phased array transducers.
Pipe welds in, for example, nuclear reactors, have been examined with ultrasonic transducers using 45° and 60° refracted longitudinal waves. These angles have been established as the “norm” based on the weld configurations, ultrasonic theory, and field experience. The pipes are raster scanned in four directions to completely examine the weld volume which is very time consuming. Problems are sometimes experienced with the setup of the manipulator that delivers the ultrasonic transducers to the weld, and more importantly with the contact between the transducers and the specimen being examined. If continuous contact between the transducer and the pipe is not maintained, the scan data collected will be flawed which can result in time consuming rescans or missed defect detections.
Phased array ultrasonic probes have been developed that increase examination efficiency of conventional ultrasonic examination techniques by electronically steering the ultrasonic beam through a given range of angles. One major problem that still exists is the contact between the phased array ultrasonic transducer and the specimen being examined. Complex gimbling mechanisms that apply downward pressure on the transducers have been used to attempt to overcome this problem. However, other issues, for example, improper scanner setup and irregularities in the pipe surface can also effect inspection accuracy.